Coated Fabric for Airbag

ABSTRACT

The purpose of the present invention pertains to a coated fabric used for an automotive airbag, and more particularly, a coated fabric for an airbag most suitable for a rollover curtain airbag which is produced applying a sealing agent to a coated fabric and sewing the resulting fabric and which can keep the adhesion of the sealing agent to the coat resin even after long-term and high-temperature aging. The present coated fabric for an airbag is obtained by applying an addition-polymerizable solvent-free silicone resin onto at least one surface of a synthetic fiber textile, wherein a coating amount of the silicone resin is 15 to 45 g/m 2 ; and a weft strain/warp strain ratio as observed in stretching the coated fabric is 0.30 to 0.65.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/914,101, filed on Feb. 24, 2016, which is a 35 U.S.C. § 371 NationalStage of International Application No. PCT/JP2014/072115, filed Aug. 25,2014, which claims priority to JP 2013-174823, filed Aug. 26, 2013, allof which are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a silicone resin coated fabric used foran automotive airbag, and more particularly, to a coated fabric which ismost suitable for a rollover curtain airbag.

BACKGROUND ART

Automotive airbags are used for the purpose of protecting an occupant'sbody such as a face, head and the like in the event of a crash byactuating a sensor following an impact, generating a high-temperatureand high-pressure gas, and instantaneously inflating an airbag with thisgas. In recent years, automotive airbags have been widely used as one ofsafety devices and have been developed in their practical use not onlyfor a driver seat and a passenger seat but also as knee airbags, sideairbags, curtain airbags, etc., and automobiles including a plurality ofairbags as standard equipment are increasing.

In association with increases of a site and quantity of an airbag to beinstalled, a request for further reduction in weight and size of anairbag system is increasing, and each part of the system has beendesigned for reducing weight and size of an airbag. In the context ofthis, a bag body of an air bag is studied for reduction of a bag volumeor reduction of weight of the airbag by employing a coating-free basefabric, but in a side bag and a curtain air bag, which are located at aposition close to a human body, use of a coated fabric is a main streambecause a developing speed is required.

Moreover, installation of an airbag addressing rollover is increasingamong curtain air bags. Characteristics of protecting a head of apassenger during rollover of a car body and maintaining an internalpressure for about 10 seconds after development of the airbag to avoid aperson from bursting out of a car, are required of the roll over curtainair bag.

Conventionally, in order to achieve retention of an internal pressurefor a long time, a base fabric has been investigated, in which thesurface of a woven fabric by hollow weave which is densely-constitutedusing a weaving machine capable of hollow weaving is coated with 50 g/m²or less on one side surface, for example, 70 g/m² on both side surfaceof a silicone resin in Example (for example, see Patent Document 1).

In the case of a hollow woven base fabric, since the outside of the bagneeds to be coated and a coating amount of a resin needs to be increasedto maintain air-tightness, a mass of the entire bag is increased, and itis not preferred from the viewpoint of weight reduction. Further, whenthe coating amount is large, there is a problem that coated surfaces arebrought into contact with each other to increase adhesion.

Then, as other means for achieving the retention of an internalpressure, a bag in which a coating amount of the base fabric is reducedby sewing two coated base fabrics with coated surfaces directed inwardwithout using a hollow woven base fabric, is investigated. In this time,as a technology of preventing gas leakage from a woven portion, a methodof applying a sealing agent to adhere to a coating resin along a sewingline in sewing two overlaid base fabrics and sewing these base fabrics,is utilized. In order to maintain the internal pressure, it is requiredthat peeling at an interface between the woven fabric and the coatingresin does not occur, and also peeling at an interface between thesealing agent and the coating resin does not occur in developing anairbag. It is preferred that there is not a failure of the sealing agentat the sealed sewn portion, but when the failure occurs, the sealingagent itself preferably cohesively fails.

Conventionally, a base fabric for an airbag in which flat yarns havingan aspect ratio of 1.2 to 2.5 are used as a thread constituting a basefabric to reduce unevenness on the surface of a coated fabric, andadhesiveness between a sealing agent to be used in a sewing line and acoating resin is improved, is investigated (for example, see PatentDocument 2). However, although the adhesiveness at the initial presentsno problem, the adhesiveness after high-temperature aging where thesealing agent is cured and the cohesive failure of the sealing agenthardly occurs, is not described at all in terms of a base fabriccharacteristic. Also there is no description in other Documents.

PRIOR ART DOCUMENT Patent Documents

-   Patent Document 1: JP-A-2011-042898-   Patent Document 2: JP-A-2008-156798

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

It is an object of the present invention to provide a coated fabric usedfor an automotive airbag, and more particularly, a coated fabric for anairbag most suitable for a rollover curtain airbag which is producedapplying a sealing agent to a coated fabric and sewing the resultingfabric and which can keep the adhesion of the sealing agent to the coatresin even after long-term and high-temperature aging.

Solutions to the Problems

The coated fabric for an airbag of the present invention capable ofsolving the above-mentioned problems consists of the followingconstitutions.

That is, the present invention is a coated fabric for an airbag obtainedby applying an addition-polymerizable solvent-free silicone resin ontoat least one surface of a synthetic fiber textile, wherein a coatingamount of the silicone resin is 15 to 45 g/m²; and a weft strain/warpstrain ratio as observed in stretching the coated fabric is 0.30 to0.65.

Furthermore, the present invention is the coated fabric for an airbag,wherein an average resin thickness of warp and weft at a vertex portionon the surface of the coated fabric is 4 μm or more.

Furthermore, the present invention is the coated fabric for an airbag,wherein a difference in the bending resistance between in warp directionand in weft direction of the coated fabric is 3 to 20 mm.

Furthermore, the preferred embodiment of the invention is a totalfineness of a yarn constituting the textile is 200 to 550 dtex, and acover factor of the textile is 1800 to 2500.

Effects of the Invention

Since the coated fabric for an airbag of the present invention keeps theadhesiveness between the coating agent and the sealing agent even afterlong-term and high-temperature aging, it can provide a base fabric mostsuitable for a rollover curtain airbag using a sealing agent at a sewingpart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an SEM photograph of a surface of a coatedfabric for an airbag of the present invention.

FIG. 2 is an illustrative view showing a position of a vertex portion(diagonally shaded area) on the textile surface in a cross-section atthe time of cutting along broken lines in FIG. 1.

MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail below.

<Synthetic Fiber Textile>

In the present invention, the synthetic fiber textile means a textilethat is woven using synthetic fiber thread. The textile is excellent inmechanical strength and has an advantage in that the thickness can bereduced. Examples of the structure of the textile include, but are notparticularly limited, plain weave, twill weave, satin weave and variantweave thereof, multiaxial weave, and the like. Among them, plain weave,which is excellent in mechanical strength, is particularly preferred.

As materials used for the synthetic fiber, aliphatic polyamide fibersuch as Nylon 66, Nylon 6, Nylon 46 or Nylon 12; aromatic polyamidefiber such as aramid fiber; and polyester fiber such as polyethyleneterephthalate, polytrimethylene terephthalate or polybutyleneterephthalate are particularly used.

Besides the above, all-aromatic polyester fiber,poly-p-phenylenebenzobisoxazole fiber (PBO fiber), ultrahigh molecularpolyethylene fiber, polyphenylene sulfide fiber, polyether ketone fiber,or the like can be used. However, when the economic efficiency is takeninto consideration, polyester fiber and polyamide fiber are preferred,and Nylon 66 is particularly preferred. In those fibers, a part of orall of them may be produced from recycled raw materials.

In these synthetic fibers, various kinds of additives may be containedfor a purpose of improving the step passing property in themanufacturing step for starting yarn or the after-processing step.Examples of the additives include an antioxidant, thermostabilizer,smoothening agent, antistatic agent, thickener, and flame retardant.Further, the synthetic fiber may be a dope-dyed yarn or a yarn that isdyed after filature. Furthermore, the cross section of a single yarn maybe any deformed cross section in addition to an ordinary round crosssection.

The monofilament fineness of the synthetic fiber is preferably 1 to 8dtex, and more preferably 3 to 7 dtex. When the fineness is 1 dtex ormore, the strength of a textile can be maintained. On the other hand,when the fineness is 8 dtex or less, the rigidity can be kept low tomaintain the package ability.

As a weaving machine in the weaving step, a water jet loom, an air jetloom, a rapier loom and the like can be employed. The water jet loomwhich can relatively easily perform a high speed weaving is preferablyused in view of enhancing productivity.

A gray fabric after weaving may be subjected to refining or a dryfinishing; however, the gray fabric is preferably passed through warmwater before drying without performing thermosetting after drying. Sincepassing through warm water causes a thread to shrink and plays a role offilling voids of the textile, there is an effect of suppressingpermeation of a resin into the textile in coating the textile with theresin, and it is possible to raise a resin film thickness to the surfaceof a base fabric. In this case, a temperature of warm water ispreferably 80 to 95° C. and the gray fabric is preferably passed throughthe warm water for 20 seconds or more. When passing for less than 20seconds, the effect of filling voids decreases.

An amount of oil solution adhering to a base base fabric before coatingthe base fabric of the present invention is preferably less than 0.2% byweight. When the amount of oil solution adhering is 0.2% by weight ormore, adhesiveness to the silicone resin is deteriorated. The amount ismore preferably 0.1% by weight or less. Even if the amount of oilsolution adhering to the base fabric is small, there is no problem, butit is preferably 0.01% by weight or more in consideration of a steppassing property.

<Coated Fabric>

As a resin with which the textile is coated, silicone-based resinshaving heat resistance, cold resistance and flame retardance arepreferred. Specific examples of the silicone-based resins includeaddition-polymerizable silicone resins or the like. Examples of theaddition-polymerizable silicone resins include dimethyl silicone rubber,methylvinyl silicone rubber, methylphenyl silicone rubber, trimethylsilicone rubber, fluorosilicone rubber, methyl silicone resin,methylphenyl silicone resin, methylvinyl silicone resin, epoxy-modifiedsilicone resin, acrylic modified silicone resin, polyester-modifiedsilicone resin and the like. Among these, an addition-polymerizablemethylvinyl silicone rubber which has rubber elasticity after curing,has excellent strength and stretching, and is advantageous in terms ofcost, is preferable.

When the silicone resin is used, a reaction curing agent may be used,and for example, platinum-based compounds such as platinum powder,chloroplatinic acid, tetrachloroplatinic acid; palladium compounds,rhodium compounds, and organic peroxides such as benzoyl peroxide,p-chlorobenzoyl peroxide and o-chloro peroxide can be used.

In order to improve the adhesiveness between the silicone resin and thebase fabric, an adhesion aid is preferably contained in the siliconeresin. Examples of the adhesion aid include at least one selected fromthe group consisting of an amino-based silane coupling agent, anepoxy-modified silane coupling agent, a vinyl-based silane couplingagent, a chloro-based silane coupling agent and a mercapto-based silanecoupling agent.

Inorganic fillers to be added to the silicone resin have been used as afiller aimed for reinforcement, viscosity adjustment, heat resistanceimprovement and flame retardance improvement of a silicone resin, andthe most typical filler is silica particles. A specific surface area ofthe silica particle is preferably 50 m²/g or more, more preferably 50 to400 m²/g, and particularly preferably 100 to 300 m²/g. When the specificsurface area is in this range, it is easy to impart excellent tearstrength characteristic to the resulting silicone cured product. Thespecific surface area is measured by a BET method. The silica particlemay be used singly or may be used in combination of two types or morethereof. Examples of the silica particle capable of being used in thepresent invention include natural substances such as quartz, bergcrystal, silica sand and diatomite; and synthetic substances such as drysilica, silica fume, wet silica, silica gel and colloidal silica.

In order to make it easy to impart better flowability to a resincomposition including a silicone resin and an additive, theabove-mentioned silica particle is preferably a hydrophobic silicaparticle in which hydrophobization treatment of the surface of thesilica particle was performed using an organic silicon compound, forexample, methylchlorosilanes such as trimethylchlorosilane,dimethyldichlorosilane or methyltrichlorosilane, orhexaorganodisilazanes such as dimethylpolysiloxane,hexamethyldisilazane, divinyltetramethyldisilazane ordimethyltetravinyldisilazane.

The content of the silica particles is preferably 10 to 20% by mass, andmore preferably 12 to 20% by mass with respect to the entire siliconeresin. When the content of the silica particles is less than 10% bymass, mechanical strength of the silicone rubber is liable todeteriorate. On the other hand, when the content of the silica particlesis more than 20% by mass, since the flowability of the resin compositionis easily reduced, workability of coating is deteriorated, and inaddition to this, the resin becomes brittle and adhesiveness tends todeteriorate.

In the present invention, a resin viscosity of a silicone resin to beused is preferably 5000 to 40000 mPa·sec, more preferably 7000 to 25000mPa·sec, and particularly preferably 8000 to 22000 mPa·sec. When theresin viscosity is less than 5000 mPa·sec, since the resin penetratesinto a woven fabric and therefore an amount of the resin present on aresin surface of a base fabric is reduced, peeling at an interfacebetween the coating agent and the sealing agent tends to occur indeveloping an airbag. On the other hand, when the resin viscosity ismore than 40000 mPa·sec, it is difficult to adjust the coating amount to45 g/m² or less. The silicone resin may be solvent-based or may besolvent-free as long as its viscosity can be adjusted to within theabove-mentioned viscosity range; however, a solvent-free silicone resinis preferred in consideration of an impact on an environment.

In addition, in the present invention, when a resin compositioncontaining an additive other than a resin is used, the viscosity of thisresin composition is also defined as “viscosity of a resin”.

Since the airbag is stored for a prolonged time in a car in anenvironment where temperature and humidity vary largely, particularly,characteristics of peeling after a long-term and high-temperature agingtest becomes an extremely important required characteristics. Thepresent invention found out to be important that the weft strain/warpstrain ratio as observed in stretching the coated fabric is 0.30 to 0.65in order to avoid the occurrence of peeling at an interface between thecoating agent and the sealing agent in developing an airbag even afterlong-term and high-temperature aging. The weft strain/warp strain ratioin stretching is more preferably 0.35 to 0.60. When the weft strain/warpstrain ratio is less than 0.30, a deformation amount in warp directionof the base fabric becomes large in developing an airbag, a joint pointat an interface between the coating agent and the sealing agent slides,and peeling at an interface occurs. On the other hand, when the weftstrain/warp strain ratio is more than 0.65, a deformation amount in weftdirection of the base fabric becomes high in developing an airbag, ajoint point at an interface between the coating agent and the sealingagent slides similarly, and peeling at an interface occurs. In bothcases, the present inventors found out that a problem of occurrence ofpeeling at an interface arises in a state after long-term andhigh-temperature aging in which curing of the sealing agent hasproceeded although the peeling does not occur in an evaluation at aninitial stage of manufacture. The weft strain/warp strain ratio of thebase fabric can be made proper by adjusting, in weaving or processing abase cloth, a crimp ratio balance between warp and weft through tensionadjustment at the time of coating.

Adjustment of the weft strain/warp strain ratio of the base fabric canbe performed at each of steps from weaving to coated fabric. Examples ofa method of reducing a warp strain amount include a) a method ofincreasing a modulus of an original yarn to be used for warp, b) amethod of increasing a tension in warp direction in weaving, c) a methodof drying and thermosetting a fabric in a tense state in warp directionduring drying after weaving, and d) a method of passing a fabric througha dry zone in a tense state in warp direction during coating. Preferredone among these methods is a method of drying and thermosetting a fabricin a tense state in warp direction during drying, or a method of passinga fabric through a dry zone in a tense state in warp direction duringcoating, and particularly preferred one is a method of passing a fabricthrough a dry zone in a tense state in warp direction during coating.This method is close to a final step of an airbag fabric, and it is notonly easy to adjust to required physical properties, but also easy toadjust a resin amount in coating, and therefore the method isparticularly preferred. When passing a fabric through a dry zone in atense state in warp direction during coating, adjustment in warp andweft directions may be performed with a predetermined tensile forceusing a pin tenter to adjust the required weft strain/warp strain ratioof a base fabric. The strain amount in weft direction can be similarlyadjusted with an original yarn to be used, a tensile force of weft inweaving, and a tensile force in drying and heat quantity.

Here, a measurement method of the weft strain/warp strain ratio will bedescribed. A woven fabric is cut into a size of 300 mm in warp directionand 55 mm in weft direction, and warps are removed by nearly equalnumber from both ends and a direction of lateral thread is adjusted to50 mm. Thereafter, a test piece is held at a chuck distance of 200 mm ina constant-speed loading type tensile tester, and a line is drawn inweft direction at a central portion of 100 mm. Thereafter, loads of 125N, 250 N, 500 N, 1000 N and 2000 N are applied to pull the test pieceand stop, respectively. Change amounts in warp direction and changeamounts in weft direction of the central portion previously marked areread. The change amount in weft direction/the change amount in warpdirection in each tensile strength is calculated, and absolute values ofthe calculated values are averaged to determine a weft strain/warpstrain ratio. In addition, a sample is taken at five locations selectedon a random basis to be measured.

In the coated fabric for an airbag of the present invention, it isimportant that an average resin thickness of warp and weft at a vertexportion on the surface of the coated fabric is 4 μm or more. Thethickness is preferably 6 μm or more. In addition, the vertex portionrefers to a part of a region formed by dividing a portion having a resinadhering thereto into three equal parts in a SEM cross sectionphotograph at the time of using SEM and taking a photograph of a cutplane portion cut out along a line 2 or 3 in FIG. 1. When this portionis less than 4 μm, it is not preferred since there is a high possibilityof the occurrence of peeling between the woven fabric and the coatingagent in developing an airbag. An upper limit of the thickness is notparticularly limited; however, when the thickness is 25 μm or more, itis not preferred since the problem that an adherence property of thesurface of a coated fabric becomes high arises.

A coating amount of resin of the coated fabric for an airbag of thepresent invention is preferably 15 to 45 g/m², and more preferably 20 to35 g/m². When the coating amount of resin is 15 g/m² or less, a requiredaverage resin thickness of warp and weft at a vertex portion on thesurface of the coated fabric is not achieved since a thickness of aresin layer applied to the surface of a woven fabric is low. On theother hand, when the coating amount is 45 g/m² or more, adhesivenessbetween the coating agent and the sealing agent can be secured, this notonly impairs the package ability of an airbag because flexibility of acoated woven fabric is deteriorated, but also a weight of the wholeairbag becomes large.

The coated fabric for an airbag of the present invention preferably hasa difference in the bending resistance in a 45° cantilever methodbetween in warp direction and in weft direction of 3 to 20 mm. Thedifference in the bending resistance is more preferably 3 to 15 mm. Whenthe difference in the bending resistance is 20 mm or more, a deformationamount in warp or weft direction of the base fabric becomes large indeveloping an airbag, an adhesion point at an interface between thecoating agent and the sealing agent tend to slide, and peeling at aninterface occurs. The difference in the bending resistance between inwarp direction and in weft direction can be made proper by making adifference in a crimp ratio between warp and weft. When the differencein the bending resistance is smaller, it is better since the deformationamount in warp or weft direction of the base fabric in developing anairbag becomes smaller. However, the difference in the bendingresistance between in warp direction and in weft direction is less than3 mm, it is required to increase a tensile force in warp direction inweaving conditions or to reduce a speed of stitching weft, resulting indisadvantageous result in terms of base fabric quality or productivity.Particularly, with respect to the base fabric quality, it is notpreferred since a problem that the adhesiveness between the woven fabricand the coating agent is deteriorated due to the occurrence of fuzzarises.

The coating base fabric of the present invention may be a both-sidedcoating base fabric in which both sides are coated; however, one sidecoating base fabric in which only one side is coated is preferred fromthe viewpoint of package ability.

In the present invention, as a method of applying a silicone resin,publicly known methods of providing coating are used. Examples of acoating method include knife coating, comma coating, die coating,gravure roll coating, kiss roll coating, spraying method, and dippingmethod.

A silicone resin composition is continuously applied onto a long textilebase fabric by knife coating, it is preferred to control a tensile forceof a base fabric in a traveling direction of the base fabric so as to be400 to 1000 N/m, preferably 400 to 800 N/m. When the tensile force ofthe base fabric is less than 400 N/m, selvage of a base fabric textileis bulky and a large difference in the coating amount is producedbetween a central portion and an end portion of the base fabric, andvariation of thickness in width direction becomes large. On the otherhand, when the tensile force of the base fabric exceeds 1000 N/m, acrimp ratio balance between warp and weft balance is lost, and not onlyit becomes difficult to keep the coating amount in both of warpdirection and weft direction in a specific range, but also it becomesdifficult to keep the weft strain/warp strain ratio in stretching thebase fabric in a specific range.

As a method of drying and curing the applied coating agent, heatingmethods commonly used such as hot air, infrared light, microwave and thelike, are used, and a hot air irradiation method is widely used in termsof cost. A heating temperature and heating time present no problem aslong as an applied silicone resin reaches a temperature adequate forcuring; however, the heating temperature and the heating time arepreferably 150 to 220° C. and 0.2 to 5 minutes, respectively.

The total fineness of a yarn constituting the textile is preferably 200to 550 dtex. When the total fineness is more than 550 dtex, since thethickness of the base fabric increases to increase the rigidity of thebase fabric, the package ability of airbag deteriorates. On the otherhand, when the total fineness is less than 200 dtex, mechanicalcharacteristics on the operation of airbag such as tensile strength andtear strength of the coated fabric are liable to be insufficient.

A cover factor constituting the textile is preferably 1800 to 2500, andmore preferably 1900 to 2450. When the cover factor is less than 1800,physical characteristics required as an airbag (tensile strength andtear strength) tends to decrease. On the other hand, when the coverfactor is more than 2500, a weaving property is difficult and therigidity is increased, and therefore the package ability tends todeteriorate. In addition, the cover factor (CF) can be calculated by thefollowing formula. In addition, a unit of the total fineness is “dtex”,and a unit of the weaving density/is “number of thread/2.54 cm”.

CF=(warp total fineness of warp)^(1/2)×warp density+(total fineness ofweft)^(1/2)×weft density

Adhesiveness between the coating agent and the sealing agent in thepresent invention can be evaluated by initial peel strength and acohesive failure rate, and peel strength and a cohesive failure rateafter aging. With respect to a range showing a desired adhesiveness, theinitial peel strength is preferably 45 N/cm or more, and more preferably50 N/cm. In addition to this, the peel strength after aging ispreferably 60 N/cm or more, and more preferably 63 N/cm. When theinitial peel strength is less than 45 N/cm and the peel strength afteraging is less than 60 N/cm, failure of the sealing agent occurs up to asewing thread hole in developing an air bag to cause air permeabilitythrough the sewing thread hole, and therefore an internal pressurerequired for protecting occupants cannot be maintained. The cohesivefailure rate is preferably 100% at the initial stage and at the stageafter aging, and when the cohesive failure rate is less than 100%, thisindicates that peeling occurs finally at an interface between thecoating agent and the sealing agent.

The sealing agent used in the present invention is preferably a roomtemperature curing silicone of an addition type or of a predominantlyaddition type. There is thermally curing silicone of an addition type assilicone of an addition type. The thermally curing silicone requires aheating step although it has an advantage that a curing time is short,and therefore a room temperature curing type is preferred.

Moreover, as silicone in the sealing agent, silicone in which an initialelongation at break after curing is 800% or more, preferably 1000 to1500% is preferably used. When extremely soft silicone is used, a jointportion has flexibility, and a volume at the time of folding can besmall.

Further, it is preferred to have tensile strength of 1.0 MPa or more asa resin physical property of the sealing agent. In the sealing agenthaving tensile strength lower than this value, there is a possibilitythat by a pressure in developing an airbag, leakage of air permeationfrom a sewn portion occurs since the strength is too low althoughcohesive failure occurs. The tensile strength is preferably 1.5 MPa ormore.

EXAMPLES

Below, by way of examples, the present invention will be morespecifically described. However, the present invention is not limited bythe following examples. Further all kinds' physical propertiesevaluation in the examples was performed with the following methods.

(1) Total Fineness

Total fineness was measured according to the method mentioned in JISL-1095 9.4.1.

(2) Filament Numbers

Filament numbers were counted from the cross-sectional picture of afilament thread.

(3) Density of Textile

Density of the textile was measured according to the method mentioned inJIS L-1096 8.6.1.

(4) Coating Weight

The weight of the coated fabric was measured according to the methodmentioned in JIS L-1096 8.4.2. Next, as a blank sample, the processingtreatment was carried out without coating with the resin under the samecondition at the coating, and then the weight of the resulting blanksample was measured according to the method mentioned in JIS L-10968.4.2. After that, the difference between the weight of the coatedfabric and the weight of the blank sample was determined as the coatingamount. Incidentally, the value was expressed in weight per 1 m² (g/m²).

(5) Average Resin Thickness at Vertex Portion on Surface of Textile

A coating base fabric was cut at a position of broken line portionindicated by 2 and 3 in FIG. 1 using a razor, a photograph of a crosssection was taken in warp direction and in weft direction using SEM, andit was printed on paper. Then, based on this photograph of the crosssection, a length of the cross section of a thread indicated by 4 inFIG. 2 was taken as 1, the length was divided into three equal parts,and a film thickness of the vertex portion (indicated by 5 in FIG. 2)was calculated. In addition, FIG. 2 is a schematic view of an SEMphotograph at a cut face of weft which was cut along a line 2 in FIG. 1.

With respect to the average film thickness, a resin portion indicated by5 in FIG. 2 was cut out from paper, and from a ratio of a mass of papercut out to a mass of the entire paper, an average film thickness wascalculated, and a value in warp direction and a value in weft directionwere averaged to determine an average film thickness. The average filmthickness was determined by rounding the first place of decimals.

(6) Weft Strain/Warp Strain Ratio

In measurement of the weft strain/warp strain ratio, a woven fabric iscut into a size of 300 mm in warp direction and 55 mm in weft direction,and warps are removed and a direction of lateral thread is adjusted to50 mm. Thereafter, a test piece is held at a chuck distance of 200 mm ina constant-speed loading type tensile tester, and a line is drawn inweft direction at a central portion of 100 mm in length. Thereafter,loads of 125 N, 250 N, 500 N, 1000 N and 2000 N are applied to pull thetest piece and stop, respectively. Change amounts in warp direction andchange amounts in weft direction of the central portion previouslymarked are read. The change amount in weft direction/the change amountin warp direction in each tensile strength is calculated, and absolutevalues of the calculated values are averaged to determine a weftstrain/warp strain ratio. In addition, a sample is taken at fivelocations selected on a random basis to be measured.

(7) Bending Resistance

A bending resistance was measured by a method according to JIS L 1096:1999 8.19. 1 A method (45° cantilever method).

(8) Initial Peel Strength and Cohesive Failure Rate

Two coated fabrics of 60 mm wide were bonded to each other with a roomtemperature curing silicone adhesive of addition curing type, havingtensile strength of 3.0 MPa and tensile elongation of 1300% as resinphysical properties, which was applied so as to be 1 mm in thickness,and left standing for 24 hours in an environment of 23° C. and 65% RH toharden the adhesive. Then, the coated fabric bonded with two coatedbonded fabrics was cut to prepare a piece of 50 mm wide, and a T-typepeel test of this piece was conducted at a chuck distance of 60 mm andat a tensile speed of 500 mm/min. A peak strength measured in this timewas taken as peel strength (N/cm), and the adhesiveness between thecoating agent and the sealing agent was represented by a ratio (%) ofcohesive failure at an adhesion interface. In addition, a cohesivefailure rate was calculated as follows. A portion where the siliconeadhesive layer was present in a thickness of 0.2 mm or more on thesample after the peel test was considered as cohesive failure. Thecohesive failure rate was calculated from an area of cohesive failureand an area of the sample subjected to the T-type peel test. Fourmeasurements were averaged to determine a cohesive failure rate.

(9) Peel Strength and Cohesive Failure Rate after Aging

Two coated fabrics of 60 mm wide were bonded to each other with a roomtemperature curing silicone adhesive of addition curing type, havingtensile strength of 3.0 MPa and tensile elongation of 1300% as resinphysical properties, which was applied so as to be 1 mm in thickness,and then left standing for 24 hours in an environment of 23° C. and 65%RH, and placed in an oven set at 110° C. and left standing for 1000hours. Then, the coated fabric bonded with two coated bonded fabrics wascut to prepare a piece of 50 mm wide, and a T-type peel test of thispiece was conducted at a chuck distance of 60 mm and at a tensile speedof 500 mm/min. A peak strength measured in this time was taken as peelstrength (N/cm), and the adhesiveness between the coating agent and thesealing agent was represented by a ratio (%) of cohesive failure at anadhesion interface. In addition, a cohesive failure rate was calculatedas follows. A portion where the silicone adhesive layer was present in athickness of 0.2 mm or more on the sample after the peel test wasconsidered as cohesive failure. The cohesive failure rate was calculatedfrom an area of cohesive failure and an area of the sample subjected tothe T-type peel test. Four measurements were averaged to determine acohesive failure rate.

Example 1

Polyamide 66 multi-filament yarn including 140 filaments in which thetotal fineness was 470 dtex was woven by plain weave in a water jetloom, and then the resulting product was subjected to a shrinkageprocessing using boiling water and a dry finishing at 130° C. In theresulting textile, the density of cloth in warp direction was 46threads/2.54 cm, the density of cloth in weft direction was 46threads/2.54 cm, and the cover factor was 1,994.

Next, an addition-polymerizable vinylmethyl silicone resin having aresin viscosity of 10000 mPa·sec was applied onto one side of the abovetextile with a floating knife coating. Then, the resin was cured at 200°C. for 1 minute to obtain a coated base fabric with a coating amount of35 g/m². An average resin thickness of warp and weft at a vertex portionon the textile surface of the obtained coated fabric was 11.3 μm, theweft strain/warp strain ratio was 0.57, and the bending resistance inwarp and weft directions were 59 mm and 67 mm, respectively. Thecharacteristics of this coated fabric were evaluated and the results areshown in Table 1. The obtained coated fabric exhibited 100% cohesivefailure of the sealing agent at the initial and after aging, and wasexcellent in adhesiveness between the coating agent and the sealingagent.

Example 2

A coated fabric for an airbag was prepared in the same manner as inExample 1 except for adjusting the coating amount of the resin afterdrying to 20 g/m², and the weft strain/warp strain ratio as a basefabric physical property was varied to 0.48. In this time, an averageresin thickness of warp and weft at a vertex portion on the textilesurface of the obtained coated fabric was 7.3 μm, and the bendingresistance in warp and weft directions were 64 mm and 72 mm,respectively. The characteristics of this coated fabric were evaluatedand the results are shown in Table 1. The obtained coated fabricexhibited 100% cohesive failure of the sealing agent at the initial andafter aging, and was excellent in adhesiveness between the coating agentand the sealing agent.

Example 3

A coated fabric for an airbag was prepared in the same manner as inExample 1 except for using polyamide 66 multi-filament yarn including 72filaments in which the total fineness was 470 dtex and adjusting thecoating amount of the resin after drying to 26 g/m², and the weftstrain/warp strain ratio as a base fabric physical property was variedto 0.52. In this time, an average resin thickness of warp and weft at avertex portion on the textile surface of the obtained coated fabric was7.1 μm, and the bending resistance in warp and weft directions were 67mm and 76 mm, respectively. The characteristics of this coated fabricwere evaluated and the results are shown in Table 1. The obtained coatedfabric exhibited 100% cohesive failure of the sealing agent at theinitial and after aging, and was excellent in adhesiveness between thecoating agent and the sealing agent.

Example 4

Polyamide 66 multi-filament yarn including 144 filaments in which thetotal fineness was 470 dtex was woven by plain weave in a water jetloom, and then the resulting product was subjected to a shrinkageprocessing using boiling water and a dry finishing at 130° C. In theresulting textile, the weaving density in warp direction was 51threads/2.54 cm, the density of cloth in weft direction was 51threads/2.54 cm, and the cover factor was 2,211. Thereafter, a coatedfabric for an airbag was prepared in the same manner as in Example 1except for adjusting the coating amount of the resin after drying to 25g/m², and the weft strain/warp strain ratio as a base fabric physicalproperty was varied to 0.42. In this time, an average resin thickness ofwarp and weft at a vertex portion on the textile surface of the obtainedcoated fabric was 8.4 μm, and the bending resistance in warp and weftdirections were 69 mm and 79 mm, respectively. The characteristics ofthis coated fabric were evaluated and the results are shown in Table 1.The obtained coated fabric exhibited 100% cohesive failure of thesealing agent at the initial and after aging, and was excellent inadhesiveness between the coating agent and the sealing agent.

Example 5

Polyamide 66 multi-filament yarn including 108 filaments in which thetotal fineness was 350 dtex was woven by plain weave in a water jetloom, and then the resulting product was subjected to a shrinkageprocessing using boiling water and a dry finishing at 130° C. In theresulting textile, the weaving density in warp direction was 55threads/2.54 cm, the density of cloth in weft direction was 55threads/2.54 cm, and the cover factor was 2,058. Thereafter, a coatedfabric for an airbag was prepared in the same manner as in Example 1except for adjusting the coating amount of the resin after drying to 36g/m², and the weft strain/warp strain ratio as a base fabric physicalproperty was varied to 0.60. In this time, an average resin thickness ofwarp and weft at a vertex portion on the textile surface of the obtainedcoated fabric was 10.8 μm, and the bending resistance in warp and weftdirections were 70 mm and 75 mm, respectively. The characteristics ofthis coated fabric were evaluated and the results are shown in Table 1.The obtained coated fabric exhibited 100% cohesive failure of thesealing agent at the initial and after aging, and was excellent inadhesiveness between the coating agent and the sealing agent.

Example 6

Polyamide 66 multi-filament yarn including 84 filaments in which thetotal fineness was 270 dtex was woven by plain weave in a water jetloom, and then the resulting product was subjected to a shrinkageprocessing using boiling water and a dry finishing at 130° C. In theresulting textile, the weaving density in warp direction was 69threads/2.54 cm, the density of cloth in weft direction was 69threads/2.54 cm, and the cover factor was 2,268. Thereafter, a coatedfabric for an airbag was prepared in the same manner as in Example 1except for adjusting the coating amount of the resin after drying to 25g/m², and the weft strain/warp strain ratio as a base fabric physicalproperty was varied to 0.37. In this time, an average resin thickness ofwarp and weft at a vertex portion on the textile surface of the obtainedcoated fabric was 10.4 μm, and the bending resistance in warp and weftdirections were 66 mm and 78 mm, respectively. The characteristics ofthis coated fabric were evaluated and the results are shown in Table 1.The obtained coated fabric exhibited 100% cohesive failure of thesealing agent at the initial and after aging, and was excellent inadhesiveness between the coating agent and the sealing agent.

Example 7

Polyamide 66 multi-filament yarn including 72 filaments in which thetotal fineness was 235 dtex was woven by plain weave in a water jetloom, and then the resulting product was subjected to a shrinkageprocessing using boiling water and a dry finishing at 130° C. In theresulting textile, the weaving density in warp direction was 73threads/2.54 cm, the density of cloth in weft direction was 73threads/2.54 cm, and the cover factor was 2,238. Thereafter, a coatedfabric for an airbag was prepared in the same manner as in Example 1except for adjusting the coating amount of the resin after drying to 24g/m², and the weft strain/warp strain ratio as a base fabric physicalproperty was varied to 0.44. In this time, an average resin thickness ofwarp and weft at a vertex portion on the textile surface of the obtainedcoated fabric was 8.9 μm, and the bending resistance in warp and weftdirections were 66 mm and 81 mm, respectively. The characteristics ofthis coated fabric were evaluated and the results are shown in Table 1.The obtained coated fabric exhibited 100% cohesive failure of thesealing agent at the initial and after aging, and was excellent inadhesiveness between the coating agent and the sealing agent.

Comparative Example 1

A coated fabric for an airbag was prepared in the same manner as inExample 1 except for adjusting the coating amount of the resin afterdrying to 14 g/m², and an average resin thickness of warp and weft at avertex portion on the textile surface of the coated fabric was varied to3.8 μm. In this time, the weft strain/warp strain ratio of the obtainedcoated fabric was 0.66, and the bending resistance in warp and weftdirections were 68 mm and 74 mm, respectively. The characteristics ofthis coated fabric were evaluated and the results are shown in Table 1.The obtained coated fabric exhibited 100% cohesive failure of thesealing agent at the initial, but did not exhibit 100% cohesive failureafter aging. The reason for this is that peeling occurred between thecoating agent and the sealing agent before the sealing agent wascohesively failed.

Comparative Example 2

A coated fabric for an airbag was prepared in the same manner as inExample 1 except that in Example 3, after weaving polyamide 66multi-filament yarn in a water jet loom, subjecting the resultingproduct to a dry finishing at 130° C., and thereafter, the product wassubjected to thermosetting at 180° C. while stretching the product by 0%in warp direction and by 1% in a crosswise direction and that thecoating amount of the resin after drying was adjusted to 21 g/m², andthe weft strain/warp strain ratio as a base fabric physical property wasvaried to 0.28. In this time, an average resin thickness of warp andweft at a vertex portion on the textile surface of the obtained coatedfabric was 5.2 μm, and the bending resistance in warp and weftdirections were 64 mm and 79 mm, respectively. The characteristics ofthis coated fabric were evaluated and the results are shown in Table 1.The obtained coated fabric did not exhibit 100% cohesive failure of thesealing agent at the initial and after aging, and was extremely low inadhesiveness between the coating agent and the sealing agent. The reasonfor this is that a deformation amount in warp direction of the basefabric became large in a peeling test and a joint point at an interfacebetween the coating agent and the sealing agent slid.

Comparative Example 3

A coated fabric for an airbag was prepared in the same manner as inExample 1 except for adjusting the coating amount of the resin afterdrying to 33 g/m² in Example 5, and the weft strain/warp strain ratio asa base fabric physical property was varied to 0.68. In this time, anaverage resin thickness of warp and weft at a vertex portion on thetextile surface of the obtained coated fabric was 10.6 μm, and thebending resistance in warp and weft directions were 71 mm and 76 mm,respectively. The characteristics of this coated fabric were evaluatedand the results are shown in Table 1. The obtained coated fabricexhibited 100% cohesive failure of the sealing agent at the initial, butdid not exhibit 100% cohesive failure after aging, and was low inadhesiveness between the coating agent and the sealing agent. The reasonfor this is that a deformation amount in weft direction of the basefabric became large in a peeling test and a joint point at an interfacebetween the coating agent and the sealing agent slid.

Example 8

A coated fabric for an airbag was prepared in the same manner as inExample 1 except that in Example 1, after weaving polyamide 66multi-filament yarn in a water jet loom, subjecting the resultingproduct to a dry finishing at 130° C., and thereafter, the product wassubjected to thermosetting at 180° C. while stretching the product by 0%in warp direction and by 1.5% in a crosswise direction and that thecoating amount of the resin after drying was adjusted to 25 g/m², andthe bending resistance in warp and weft directions as a base fabricphysical property were varied to 62 mm and 84 mm, respectively. In thistime, an average resin thickness of warp and weft at a vertex portion onthe textile surface of the obtained coated fabric was 8.4 μm, and theweft strain/warp strain ratio was 0.42. The characteristics of thiscoated fabric were evaluated and the results are shown in Table 1. Theobtained coated fabric exhibited 100% cohesive failure of the sealingagent at the initial. The obtained coated fabric did not exhibit 100%cohesive failure after aging. The reason for this is that since adifference in the bending resistance between in warp direction and inweft direction was large, a deformation amount in warp direction of thebase fabric became large in a peeling test and a joint point at aninterface between the coating agent and the sealing agent slid.

TABLE 1 Example Example Example Example Example Example ExampleComparative Comparative Comparative Example 1 2 3 4 5 6 7 Example 1Example 2 Example 3 8 Total fineness dtex 470 470 470 470 350 270 235470 470 350 470 Filament numbers thread 140 140 72 144 108 84 72 140 72108 140 Density of textile thread/ 46/46 46/46 46/46 51/51 55/55 69/6973/73 46/46 46/46 55/55 46/46 (warp/weft) 2.54 cm Cover factor — 1,9941,994 1,994 2,211 2,058 2,268 2,238 1,994 1,994 2,058 1,994 Coatingweight g/m² 35 20 26 25 36 25 24 14 21 33 25 Tension of base N/m 600 700680 650 800 600 610 1400 700 1100 800 fabric at the time of coatingAverage resin μm 11.3 7.3 7.1 8.4 10.8 10.4 8.9 3.8 5.2 10.6 8.4thickness at vertex portion on surface of textile Weft strain amount/ —0.57 0.48 0.52 0.42 0.60 0.37 0.44 0.66 0.28 0.68 0.42 Warp strainamount Bending resistance mm 59/67 64/72 67/76 69/79 70/75 66/78 66/8168/74 64/79 71/76 62/84 (warp/weft) Difference in mm 8 8 9 10 5 12 15 615 5 22 bending resistance Initial peel N/cm 51 50 51 51 53 57 55 43 4951 47 strength Initial cohesive % 100 100 100 100 100 100 100 100 95 100100 failure Peel strength N/cm 65 63 64 63 65 65 67 55 57 59 57 afteraging Cohesive % 100 100 100 100 100 100 100 70 66 80 95 failure rateafter aging

INDUSTRIAL APPLICABILITY

Since the coated fabric for an airbag of the present invention keeps theadhesiveness between the coating agent and the sealing agent even afterlong-term and high-temperature aging, it can provide a base fabric mostsuitable for a rollover curtain airbag using a sealing agent at a sewingpart, and therefore the coated fabric largely contributes to industries.

DESCRIPTION OF REFERENCE SIGNS

-   -   1: Coating base fabric    -   2: Direction of weft cut plane    -   3: Direction of warp cut plane    -   4: Cross-section of weft    -   5: Vertex portion

1. A coated fabric for an airbag, comprising a synthetic textile fiberand an addition-polymerized silicone resin on at least one surface ofthe synthetic fiber textile, wherein the fabric has a coating amount ofthe silicone resin of 15 to 45 g/m², an average resin thickness of warpand weft at a vertex portion on the surface of the coated fabric of 4 μmor more and 25 μm or less, and an average ratio of strain of the coatedfabric in weft direction to strain of the coated fabric in warpdirection of 0.30 to 0.65 as observed in stretching the coated fabric inthe warp direction.
 2. The coated fabric for an airbag according toclaim 1, wherein an average resin thickness of warp and weft at a vertexportion on the surface of the coated fabric is 6 μm or more.
 3. Thecoated fabric for an airbag according to claim 1, wherein a differencein the bending resistance between in warp direction and in weftdirection of the coated fabric is 3 to 20 mm.
 4. The coated fabric foran airbag according to claim 1, wherein a total fineness of a yarnconstituting the textile is 200 to 550 dtex.
 5. The coated fabric for anairbag according to claim 1, wherein a cover factor of the textile is1800 to
 2500. 6. The coated fabric for an airbag according to claim 2,wherein a difference in the bending resistance between in warp directionand in weft direction of the coated fabric is 3 to 20 mm.
 7. The coatedfabric for an airbag according to claim 2, wherein a total fineness of ayarn constituting the textile is 200 to 550 dtex.
 8. The coated fabricfor an airbag according to claim 3, wherein a total fineness of a yarnconstituting the textile is 200 to 550 dtex.
 9. The coated fabric for anairbag according to claim 6, wherein a total fineness of a yarnconstituting the textile is 200 to 550 dtex.
 10. The coated fabric foran airbag according to claim 2, wherein a cover factor of the textile is1800 to
 2500. 11. The coated fabric for an airbag according to claim 3,wherein a cover factor of the textile is 1800 to
 2500. 12. The coatedfabric for an airbag according to claim 4, wherein a cover factor of thetextile is 1800 to
 2500. 13. The coated fabric for an airbag accordingto claim 6, wherein a cover factor of the textile is 1800 to
 2500. 14.The coated fabric for an airbag according to claim 7, wherein a coverfactor of the textile is 1800 to
 2500. 15. The coated fabric for anairbag according to claim 8, wherein a cover factor of the textile is1800 to
 2500. 16. The coated fabric for an airbag according to claim 9,wherein a cover factor of the textile is 1800 to 2500.